Distribution systems utilized by electric power utilities generally consist of a power distribution grid having a control station, a power source, such as a substation, connected to a plurality of terminal nodes by grid branches, generally power wires, and corresponding protective devices, such as fuses or breakers, set up along the grid branches and designed to operate when a fault in the power distribution grid occurs, to ensure that only a minimal portion of the system is affected by the resulting power outage. During major storms, utilities track and prioritize power outages, dispatch and coordinate the labor force, and direct system restoration. In order to identify a power outage, determine the location of the fault that caused it, and estimate the number of affected customers, information from several different utility information systems must be combined and analyzed. In an effort to improve information feedback on their facilities and service reliability in general, utilities are developing and implementing geographic information systems (GIS) based automated mapping/facilities management (AM/FM) systems. Integration of GIS-based AM/FM systems with customer information systems (CIS) as well as supervisory control and data acquisition (SCADA) systems provides the optimal environment for an outage management system (OMS).
An OMS is, thus, a decision support environment that can be used to address complex problems faced by distribution dispatchers and system operators in an emergency situation. In an integrated environment obtained by combining information from GIS-based AM/FM systems, CIS, and SCADA systems, the OMS allows concurrent processing of data from multiple sources. Information from customer calls, received and logged in trouble order tracking (TOT) systems, or reports from other monitoring sources such as power outage monitors (so-called intelligent electronic devices) or automated meter reading systems that automatically contact the control station after loss of power is identified, distribution network topology, and protective device schema derived from GIS coverage maps, are combined to determine the probable fault location. In addition, the OMS can process power outages reported by SCADA alarms or field crew reports called in by radio.
Once a power outage is identified or reported, it is processed to determine the number of customers without power, checked for the existence of life-supporting devices, and sorted according to priorities that help dispatchers optimally dispatch crews. The OMS maintains current information on power outages, dynamically provides users with suggestions on the probable causes of power outages, and associates a level of confidence with its determination. The geographically referenced full graphic environment acts as an electronic "pin map" to display locations of trouble calls and determine the causes of power outages. At the same time, the geographically referenced full graphic environment allows the user to select, query, and update information associated with power outages and trouble calls.
When applied to customer calls reporting power outages, the OMS begins the process of power outage determination by analyzing all incoming calls and locating the caller's connection to the distribution network. First, the graphic display can mark the location of the trouble call with a special symbol. This creates an electronic "pin map" of the deenergized customers. Outage determination (OD) achieves a progressively higher confidence factor in establishing the protective device that is likely to have operated as a result of the fault causing the power outage as more calls come in. OD evaluates the protection schemes derived from GIS map coverages and compares them with the incoming calls. The OMS can be programmed such that, upon reaching a specified level (threshold) of confidence, the location of the fault causing the power outage is automatically determined. OMS can also be run in a semiautomatic mode, which can continuously update the OMS operator to the current confidence factor and allow the operator to make the final determination. Power outages reported from SCADA devices can be shown on the OMS display using different graphic symbols or colors from those used for the power outage reports that have come from the OD module, if desired. After the cause of the power outage is determined by the OMS power outage determination procedure, or reported by the SCADA alarms or a field crew by radio, the outage-processing procedure continues the analysis by identifying a list of customers affected, combining network connectivity maintained in GIS and customer data from the CIS.
The quality of an automated OMS depends highly on the inferencing power of the computerized OD procedure. To model the uncertainty involved with locating the probable location of a fault causing a power outage, appropriate tools and methods are needed. The conventional way to deal with uncertainty is to use tools and methods provided by the theory of probability. However, probability is an appropriate measure of uncertainty only in cases where statistical information is available. Therefore, current computerized OD procedures are unable to properly model the inexactness and uncertainty associated with locating faults due to the lack of distribution system information sufficient to form a statistical basis for inferring a confidence factor with any degree of success.
Accordingly, it is evident that there is a need for a method and apparatus for power outage determination using distribution system information that demonstrates superior inferencing power in modeling the uncertainty involved with determining the probable location of the fault causing a power outage. Such a method and apparatus should be able to more accurately model the uncertainty involved with determining the probable location of the fault using the same distribution system information available to current OMSs. The present invention is directed to fulfilling this need.